Modification of the head proteome of nurse honeybees (Apis mellifera) exposed to field-relevant doses of pesticides.

Understanding the effect of pesticides on the survival of honeybee colonies is important because these pollinators are reportedly declining globally. In the present study, we examined the changes in the head proteome of nurse honeybees exposed to individual and combined pesticides (the fungicide pyraclostrobin and the insecticide fipronil) at field-relevant doses (850 and 2.5 ppb, respectively). The head proteomes of bees exposed to pesticides were compared with those of bees that were not exposed, and proteins with differences in expression were identified by mass spectrometry. The exposure of nurse bees to pesticides reduced the expression of four of the major royal jelly proteins (MRJP1, MRJP2, MRJP4, and MRJP5) and also several proteins associated with carbohydrate metabolism and energy synthesis, the antioxidant system, detoxification, biosynthesis, amino acid metabolism, transcription and translation, protein folding and binding, olfaction, and learning and memory. Overall, when pyraclostrobin and fipronil were combined, the changes in protein expression were exacerbated. Our results demonstrate that vital proteins and metabolic processes are impaired in nurse honeybees exposed to pesticides in doses close to those experienced by these insects in the field, increasing their susceptibility to stressors and affecting the nutrition and maintenance of both managed and natural colonies.

Using enzyme activities and soil microbial diversity to understand the effects of fluoxastrobin on microorganisms in fluvo-aquic soil.

Whether now or in the foreseeable future, agricultural production cannot do without chemical pesticides. Strobilurin fungicides, including mitochondrial inhibitors, can easily enter the soil environment and causing pollution. Fluoxastrobin is one of the top-selling strobilurin fungicides. Limited information can be found in the literature on the environmental toxicity of fluoxastrobin in soil. It is essential to understand the effects of fluoxastrobin on microorganisms in fluvo-aquic soil. The present study used a Biolog-EcoPlate method to analyze the effects of fluoxastrobin on soil microbial diversity in groups exposed to 0.1, 1.0, and 2.5 mg/kg fluoxastrobin and in control groups at exposure and on days 7, 14, 21, 28, and 48. The effects of fluoxastrobin on enzyme activities (ß-glucosidase, dehydrogenase, and urease) in the soil were also evaluated. The results indicated that the three tested enzyme activities were lower at each dose to a varying degree than those of the controls. The soil microbial diversity was shown to be affected according to the results of average well color development (AWCD) experiments. The present study aimed to assess environmental risks to terrestrial ecosystems under the stress of pesticide use. These results also enrich the basic data on fungicide toxicity to the soil environment and have a guiding significance for the rational use of pesticides and the sustainable utilization of resources.

Developmental toxicity, oxidative stress and immunotoxicity induced by three strobilurins (pyraclostrobin, trifloxystrobin and picoxystrobin) in zebrafish embryos.

Strobilurins is the most widely used class of fungicides, but is reported highly toxic to some aquatic organisms. In this study, zebrafish embryos were exposed to a range concentrations of three strobilurins (pyraclostrobin, trifloxystrobin and picoxystrobin) for 96 h post-fertilization (hpf) to assess their aquatic toxicity. The 96-h LC50 values of pyraclostrobin, trifloxystrobin and picoxystrobin to embryos were 61, 55, 86 µg/L, respectively. A series of symptoms were observed in developmental embryos during acute exposure, including decreased heartbeat, hatching inhibition, growth regression, and morphological deformities. Moreover, the three fungicides induced oxidative stress in embryos through increasing reactive oxygen species (ROS) and malonaldehyde (MDA) contents, inhibiting superoxide dismutase (SOD) activity and glutathione (GSH) content as well as differently changing catalase (CAT) activity and mRNA levels of genes related to antioxidant system (Mn-sod, Cu/Zn-sod, Cat, Nrf2, Ucp2 and Bcl2). In addition, exposure to the three strobilurins resulted in significant upregulation of IFN and CC-chem as well as differently changed expressions of TNFa, IL-1b, C1C and IL-8, which related to the innate immune system, suggesting that these fungicides caused immunotoxicity during zebrafish embryo development. The different response of enzymes and genes in embryos exposed to the three fungicides might be the cause that leads to the difference of their toxicity. This work made a comparison of the toxicity of three strobilurins to zebrafish embryos on multi-levels and would provide a better understanding of the toxic effects of strobilurins on aquatic organisms.

Suppression of wheat Fusarium head blight by novel amphiphilic aminoglycoside fungicide K20.

K20 is a novel amphiphilic aminoglycoside capable of inhibiting many fungal species. K20's capabilities to inhibit Fusarium graminearum the causal agent wheat Fusarium head blight (FHB) and to this disease were examined. K20 inhibited the growth of F. graminearum (minimum inhibitory concentrations, 7.8-15.6 mg L-1) and exhibited synergistic activity when combined with triazole and strobilurin fungicides. Application of K20 up to 720 mg L-1 to wheat heads in the greenhouse showed no phytotoxic effects. Spraying wheat heads in the greenhouse with K20 alone at 360 mg L-1 lowered FHB severity below controls while combining K20 with half-label rates of Headline (pyraclostrobin) improved its disease control efficacy. In field trials, spraying K20 at 180 mg L-1 and 360 mg L-1 combined with half-label rates of Headline, Proline 480 SC (prothioconazole), Prosaro 421 SC (prothioconazole + tebuconazole), and Caramba (metconazole) reduced FHB indices synergistically. In addition, the K20 plus Proline 480 SC combination reduced levels of the mycotoxin deoxinivalenol by 75 % compared to the control. These data suggest that K20 may be useful as a fungicide against plant diseases such as FHB particularly when combined with commercial fungicides applied at below recommended rates.

Pyraclostrobin Impairs Energetic Mitochondrial Metabolism and Productive Performance of Silkworm (Lepidoptera: Bombycidae) Caterpillars.

Silkworm cocoon production has been reduced due to a number of problems other than those inherent in sericulture, such as diseases, malnutrition, and inappropriate management. The use of pesticides in areas surrounding mulberry fields can contaminate these plants and consequently harm caterpillars. The aim of this study was to evaluate whether the application of the fungicide pyraclostrobin in mulberry plants interferes with the mitochondrial bioenergetics and the productive performance of silkworms. Mulberry plants were treated with pyraclostrobin (0, 100, 200, and 300 g ha-1). After 30 d of fungicide application, fifth instar caterpillars were fed with leaves from the treated plants. We evaluated in vitro and in vivo mitochondrial bioenergetics of mitochondria from the head and intestines, as well as the feed intake and mortality rate of the caterpillars and the weight of fresh cocoons and cocoons shells. At doses of 50 µM (in vitro) and 200 g ha-1 (in vivo), pyraclostrobin inhibited oxygen consumption in state 3, dissipated membrane potential, and inhibited ATP synthesis in mitochondria. Pyraclostrobin acted as a respiratory chain inhibitor, affecting mitochondrial bioenergetics. The fungicide did not interfere with food consumption but negatively affected mortality rate and weight of cocoons. Mulberry leaves contaminated with pyraclostrobin negatively impact the mitochondrial bioenergetics of silkworms and cocoon production.